Filters and interceptors are both powerful tools in Java for intercepting requests and responses, but they serve different purposes and operate at different stages of the request lifecycle.
Filters
Filters are used to intercept requests before they reach the servlet or other resources. They operate at the request processing phase and can be used to:
- Authentication: Verify user credentials before allowing access to protected resources.
- Authorization: Determine if a user has the necessary permissions to access a resource.
- Logging: Record request details for debugging or auditing purposes.
- Compression: Compress response data to improve performance.
- Encoding: Encode or decode request or response data.
Example: A filter could check for a valid session ID before allowing access to a protected page.
Interceptors
Interceptors, on the other hand, are used to intercept requests within a specific method of a controller or service. They operate at the method invocation phase. Interceptors are commonly used for:
- Transaction management: Ensure that database operations are wrapped within a transaction.
- Logging: Log method calls and their parameters.
- Validation: Validate input data before processing.
- Caching: Cache method results to improve performance.
- Security: Implement access control or authentication at the method level.
Example: An interceptor could log the start and end times of a method call, along with the method's parameters and return value.
Key Differences
Here is a table summarizing the key differences between filters and interceptors:
| Feature | Filter | Interceptor |
|---|---|---|
| Operation Stage | Request processing phase | Method invocation phase |
| Target | Entire request | Specific method |
| Scope | Global | Local to a specific controller or service |
| Typical Use Cases | Authentication, authorization, logging, compression, encoding | Transaction management, logging, validation, caching, security |
Conclusion
In summary, filters are used to intercept requests at the request processing phase, while interceptors are used to intercept requests at the method invocation phase. Choosing between filters and interceptors depends on the specific use case and desired functionality.
